Biopellets vs. Denitrating Reactor

[Corsair]

Getting all the final bits together before retrofitting the sump onto my 20L and I could use a bit of guidance. I have a phos-ban reactor that I can set up one of two ways. Either blow lots of water through and use biopellets, or barely any and use a denitrating media. I'm just trying to get a feel for the pros and cons of each approach.

 

So as far as bio-pellets, if I'm understanding it correctly both nitrates and phosphates are being consumed to create bacteria. No nutrients are "removed" per se, just sequestered in the bodies of the bacteria which are hopefully skimmed or consumed before they die and release the nutriants again.

 

I'm going to be using an Aquatic Life 115, so my skimming capacity won't be mega-huge. As a practical consideration, that means a large amount of bacteria will likely find it's way back into the display. On paper that seems great, as I have lots of filter feeding soft corals, and wouldn't mind adding more specialized critters like feather dusters. Do the types of bacteria emitted by the reactor provide any real nutrition to my corals? Do they consume it fairly quickly, or is the skimmer size a big limiting factor on the effectiveness of biopellets?

 

Now as for the denitrating approach, I guess this is another way of approaching the use of solid bacteria food? What I'm talking about is products like Seachem De*Nitrate, or Kent Nitrogen Sponge. If I'm reading right you want to barely trickle water through, and something in the media helps to grow anaerobic bacteria. Something presumably consumed as a portion of the media is periodically replaced. On paper it looks great, but if it was that simple why isn't it more common?

 

I'm still new at this and I'm trying to get a feel for how these bacteria really perform in the real world. I could definitely stand to hear from some of you who have done this before.

 

Thanks!

-Aaron

[sean151]

I think you misunderstand what bacteria is. It's not a food source, just something that eats away at nitrogen based compounds in conjunction with phosphate. Bacteria in the tank stays on surfaces, in this case biopellets and your lr. The Aquatic Life 115 is plenty to work in conjunction with carbon dosing so that is not an issue to worry about as I have seen plenty of threads and comments of people doing so. Carbon dosing is not something you should do early into your reef tank is you need to at all because it takes a good deal of research to really know what you are getting into before you don't screw up your whole tank irreversibly.

[mikellini]

Also, the nitrates don't exactly get consumed to grow bacteria the way you think. Denitrifying bacteria convert nitrates (NO3) into nitrogen and oxygen as part of their metabolism. So when the bacteria die, they don't necessarily re-release the nitrates that they have "consumed", because they didn't really consume anything, they processed it.

[Corsair]

There is a really excellent chance I'm misunderstanding something. From what I've read about biopellets, it's compared to "solid vodka dosing" and grows mostly aerobic bacteria. If nitrates are going down and oxygen is being consumed, it seems unlikely the nitrates are being reduced to N2. The product manufactures claim the coral feeding benefit. Bacteria is described as "sloughing off" the pellet surfaces. If I'm not getting it please straighten me out. This is the one I was looking at

 

 

The other option with this reactor seems to be this type of media

 

 

Which from the manufacturer info is supposed to sit in a very low flow environment so that it makes a big anaerobic zone. I get that this environment would actually break down the nitrates into N2. My thought that it was a solid "food" of some sort was a guess from the fact that it had to be replaced every so often. Unless it is inert stuff (and presumably useless) it must be providing something to the process. I just haven't found many documented cases of long term success.

 

I'm not really comfortable vodka dosing at all. My schedule is just too inconsistent to keep up with regular dosing. Avoiding that is my goal in setting this system up.

[mikellini]

I do know that some saltwater aerobic bacteria do accomplish some denitrification; they're just not very efficient at it. I admittedly don't know much about the two products you're talking about, but I can't see any reason to forgo using live rock, sand, and plants (macroalgae or something like mangrove) as your primary filtration. At least, as long as you're interested in biological methods.

[Corsair]

The display itself already has a relatively large amount of rock and macro. The sump is small and without baffles due to space restrictions in the stand, so no fuge. Everything stays more or less stable at 20ppm nitrates with weekly water changes. Not enough to bother much of anything living in there, though I'd prefer it be closer to 5-10ppm. The skimmer alone might do that, but I have lots of pumps laying around, and the reactor was cheap so I figured I'd give this a shot.

 

The di*nitrate media looks the easiest. It's cheaper, and my need for nitrate reduction isn't urgent, so I can wait for the thing to cycle. I really have no issues with phosphates, so I don't need help there. The potential advantage with the bio pellets in my mind is the prospect of using "waste" nutrients to produce food for the corals. I just don't know if that's really how it works.

[drainbamage]

the idea of a carbon source such as the biopellets is to grow/encourage the growth of bacteria strains that consume both nitrate and the carbon source. Once these bacteria's die, your skimmer needs to be strong enough to remove them from the water column before they break down (essentially re-adding to the nitrate level.) Thus vodka dosers/bio-pellet people NEED to have a very good skimmer on the system.

 

A nitrate reactor works via a different process (though some of the 'trate 'sponges' are different than a true 'trate reactor.) Here the idea is to create a condition that is anaerobic (opposite of most all of our tanks area excepting a few small pockets within the live rock structure) to grow the bacteria that consumes nitrate and turns it into gaseous nitrogen (hence calling it the nitrogen cycle, not the nitrate cycle, lol.) These reactors require very slow flow to prevent the buildup of oxygen in them, too much of the O and you're going to wipe out these bacteria cultures.

 

I've never played that in depth with the different reactor medias for doing a 'trate reactor, so can't offer you a lot of advice there- I'm a vodka doser and have zero desire to change from it. It's a bit more upkeep (having to remember to add vodka daily/ever couple of days) but has given me very nice results so far, though i do still do the occasional water change (just a believer in flushing in new water every so often for all the different variables it affects.)

[swigen]

the idea of a carbon source such as the biopellets is to grow/encourage the growth of bacteria strains that consume both nitrate and the carbon source. Once these bacteria's die, your skimmer needs to be strong enough to remove them from the water column before they break down (essentially re-adding to the nitrate level.) Thus vodka dosers/bio-pellet people NEED to have a very good skimmer on the system.

 

According to this article (http://www.advancedaquarist.com/2011/3/aafeature), a skimmer can remove only about 30-40% of the bacteria in the water column.

 

Carbon dosing is not something you should do early into your reef tank is you need to at all because it takes a good deal of research to really know what you are getting into before you don't screw up your whole tank irreversibly.

 

With solid carbon dosing is there really that much risk to your tank? I mean the bacteria's already there, if carbon is limiting, they will take advantage of the solids, if not, they won't. Can you explain how using biopellets could "screw up your whole tank irreversibly."

[paneubert]

With solid carbon dosing is there really that much risk to your tank? I mean the bacteria's already there, if carbon is limiting, they will take advantage of the solids, if not, they won't. Can you explain how using biopellets could "screw up your whole tank irreversibly."

 

Solid would be less of an issue than liquid. The risk taken is that if you stop dosing liquid suddenly, the bacteria population on your glass/rock/sand can crash from sudden lack of a carbon source. With solid, if you removed it all at once, there would be less of a risk since the theoretical huge bacterial population was mostly in the solid media that was removed.

 

At least that is my theory.

[Corsair]

the idea of a carbon source such as the biopellets is to grow/encourage the growth of bacteria strains that consume both nitrate and the carbon source. Once these bacteria's die, your skimmer needs to be strong enough to remove them from the water column before they break down (essentially re-adding to the nitrate level.) Thus vodka dosers/bio-pellet people NEED to have a very good skimmer on the system.

 

Ok, so sounds like I'm more or less on the right page as far as the pellets then. Basically just binding up the nutrients in the form of bacteria for removal by skimming or predation. I've heard the figure of 30-40% before, and the Aqutic Life skimmer is good, but not a rockstar. If there is an additional benefit of the bacteria feeding tank inhabitants that would be nice. I just don't know enough about the ecology of the thing to know how useful that food source is.

 

A nitrate reactor works via a different process (though some of the 'trate 'sponges' are different than a true 'trate reactor.) Here the idea is to create a condition that is anaerobic (opposite of most all of our tanks area excepting a few small pockets within the live rock structure) to grow the bacteria that consumes nitrate and turns it into gaseous nitrogen (hence calling it the nitrogen cycle, not the nitrate cycle, lol.) These reactors require very slow flow to prevent the buildup of oxygen in them, too much of the O and you're going to wipe out these bacteria cultures.

 

I think the De*Nitrate is supposed to host bacteria, as opposed to Purigen which directly removes it. It really sounds like a coil de-nitrator without the coil. Presumably the lower portion is aerobic, and the upper portion is anearobic. I have a MiniJet 404 that turned all the way down would probably be slow enough. It goes down to 20gph, and has to push about 14" of head to enter the reactor.

 

I've seen people fill reactors with bioballs and dose with VSV (vodka, sugar, vinegar?) to feed the bacteria. That seems to be the same principle. Something in the De*Nitrate must be replacing the VSV (if it works), so you can infer that the de-nitrators are a different sort of "bacteria food." Honestly it seems like both approaches are just an evolution of the coil reactor that uses food to increase population density. That lets you simplify construction and/or increase the flow rate.

 

Or I'm completely off.

[sean151]

Solid would be less of an issue than liquid. The risk taken is that if you stop dosing liquid suddenly, the bacteria population on your glass/rock/sand can crash from sudden lack of a carbon source. With solid, if you removed it all at once, there would be less of a risk since the theoretical huge bacterial population was mostly in the solid media that was removed.

 

At least that is my theory.

This is exactly what I meant. Also, if the person doesn't know what they are doing they may not feed heavy enough as you have to increase feeding if you are to use carbon dosing or else it may pastel your sps, which may be a plus to some people I guess. Also, most run it alongside a GFO reactor to take out excess phosphate just a little heads up to the OP on another thing to think about.

[swigen]

This is exactly what I meant. Also, if the person doesn't know what they are doing they may not feed heavy enough as you have to increase feeding if you are to use carbon dosing or else it may pastel your sps, which may be a plus to some people I guess. Also, most run it alongside a GFO reactor to take out excess phosphate just a little heads up to the OP on another thing to think about.

 

So, not really a risk to "irreversibly screw up your tank" then?

 

I understand there could be a die off of some bacteria if you were to stop dosing, but would there really be that much nutrients bound up in just bacteria to cause a crash? Know of any examples of a tank crash as a result of bacteria die off because carbon becomes limited AGAIN?

[Corsair]

So, not really a risk to "irreversibly screw up your tank" then?

 

I understand there could be a die off of some bacteria if you were to stop dosing, but would there really be that much nutrients bound up in just bacteria to cause a crash? Know of any examples of a tank crash as a result of bacteria die off because carbon becomes limited AGAIN?

 

No, I bet you could screw it up pretty good. With the pellets you have the process mostly centralized, and the food doesn't run out. If you were dosing carbon and cut it off, it would be bad news. The reason the dosing works is that it massively increases the bacteria populations. Sometimes apparently to the point where you can see big clumps of them (!!!).

 

It's conceptually not too far off from using macroalgea for nutrient control. The only way the bacteria can remove any nutrients from the water column is:

-ending up in a skimmer cup

-being consumed by something (what?) and metabolized into its body.

 

The point I'm really stuck on is how useful the addition of the bacteria is as food. I think the existing load in the display might be enough for the skimmer to handle without expecting it to keep up with a biopellet reactor. Is it reasonable to think that a population of zooplankton will rise once they have a food source, and so on up the macro chain until you get to big enough stuff for the corals to thrive on? Is that what you see with long term vodka dosing?

 

 

This is exactly what I meant. Also, if the person doesn't know what they are doing they may not feed heavy enough as you have to increase feeding if you are to use carbon dosing or else it may pastel your sps, which may be a plus to some people I guess. Also, most run it alongside a GFO reactor to take out excess phosphate just a little heads up to the OP on another thing to think about.

[paneubert]

I understand there could be a die off of some bacteria if you were to stop dosing, but would there really be that much nutrients bound up in just bacteria to cause a crash? Know of any examples of a tank crash as a result of bacteria die off because carbon becomes limited AGAIN?

 

I do not have any specific links, but I can assure you that if you were dosing liquid, and stopped, there is a very real chance of a crash. You have to back the dosing off slowly if you plan to stop. I HAVE read of specific people having a crash happen, but I am not ambitious enough to go find those examples I read tons of them when I was first researching carbon dosing.

[swigen]

I do not have any specific links, but I can assure you that if you were dosing liquid, and stopped, there is a very real chance of a crash. You have to back the dosing off slowly if you plan to stop. I HAVE read of specific people having a crash happen, but I am not ambitious enough to go find those examples I read tons of them when I was first researching carbon dosing.

 

Ok, so it fair to say that solid carbon dosing is a safer version of the liquid (vodka, etc) carbon dosing methods?

 

The reason I ask so many questions is becuase i too am thinking about running some biopellets. I chose the solid carbon dosing since it seems easier to maintain (no daily dosing) and there are less risks associated with overdosing, massive bacteria population die offs, etc.

[mikellini]

I just started reading up on this... Took a bit of a break and hadn't heard of biopellets but it seems to be an effective method for reducing n&p. But it seems it isn't mature yet, at least in the aquarium industry

[sean151]

Ok, so it fair to say that solid carbon dosing is a safer version of the liquid (vodka, etc) carbon dosing methods?

 

The reason I ask so many questions is becuase i too am thinking about running some biopellets. I chose the solid carbon dosing since it seems easier to maintain (no daily dosing) and there are less risks associated with overdosing, massive bacteria population die offs, etc.

This is exactly why there are many people tooting this as a breakthrough in reefing. You can't overdose it and it's more of a set and forget setup where the chance of messing up is minimized greatly. A reefer could essentially set up a reactor and then not pay much attention to it besides making sure it works on occasion where vodka/sugar/whatever has to be applied consistently once you get the levels up high enough and is usually a daily chore that would tie someone to their tank.

[Aquanist]

I've been using biopellets for nearly a year now, and they do actually work. In the first month or so as the bacteria colonizes pellets the drop in NO3 can be easily measured. Although they're not the gateway to instant state of bliss and joy they surely help keeping the nitrates down and allow heavier feeding while still having lower (or same) NO3 levels as before.

 

While there is no risk of tank crashing due to overdosing, it is possible that using too much biopellets compared to tank and skimmer size, it can cause a bacterial bloom resulting in cloudy water. This does usually go away in a week as the bacteria levels stabilize. It is recommended to have media reactor exhaust near skimmer intake to minimize the chances for this to happen and to catch the bacteria die-off.

 

Not all freefalling bacteria is (nor should IMO) removed from the water column by skimming and this should (at least by marketing people) provide an excellent food source for both corals and fishes as this bacteria build-up breaking away from pellet surface should be right size etc.. I really don't know the science behind this, but my own experience with this suggests the it does provide corals at least with some additional nutrition. I have LPS feeding at all hours even when I'm not adding any food myself. And SPS seem to like it as well as polyp extension has been far more significant after starting to use biopellets.

 

All above are just my own experiences on my own tank.

[Corsair]

Ordered 200mL of TLF pellets last night, along with some of the miscellanea I need to complete the plumbing. I'll post updates on construction in my tank thread when I get a little farther along. One more question though, regarding this:

 

Also, most run it alongside a GFO reactor to take out excess phosphate just a little heads up to the OP on another thing to think about.

 

So far I've had no issues with phosphates. I guess it's all the calurpa growing wild that keeps it in check, but between the macro and a small bag of chemi-pure it's been a non-issue. I thought the pellets helped reduce phosphates, honestly I was hoping to not use the chemi-pure either once this thing got going. Am I likely to run into PO4 troubles later down the line?

[gojk]

I use the TLF biopellets and my N and Ps dropped to zero for the first time ever in my tank and I have been feeding twice as much or more than I was in the past. They certainly do work.

[Corsair]

I use the TLF biopellets and my N and Ps dropped to zero for the first time ever in my tank and I have been feeding twice as much or more than I was in the past. They certainly do work.

 

 

That seems to be the consensus with most of what I've read online. When the biopellets are working right, PO4 drops like a stone. I'd love to eliminate the chemical filtration on this tank. My background is low-tech f/w planted tanks, and I never considered them to be in equilibrium until I could pull the carbon and leave it out.

[sean151]

There are some users who seem to have it drop but then go back up as the nitrate stays consistently zero. It has to do with the uptake ratio of nitrogen to phosphorous. Usually shows up through cyano and such, but with macros in the tank to you should have no problems at all with it.